Increased co-first authorships in biomedical and clinical publications: a call for recognition.

There has been a dramatic increase in the number and percentage of publications in biomedical and clinical journals in which two or more coauthors claim first authorship, with a change in some journals from no joint first authorship in 1990 to co-first authorship of >30% of all research publications in 2012. As biomedical and clinical research become increasingly complex and team-driven, and given the importance attributed to first authorship by grant reviewers and promotion and tenure committees, the time is ripe for journals, bibliographic databases, and authors to highlight equal first author contributions of published original research.